1. Technical Field
The present invention relates generally to a digital communication system for wireless mobile communication terminals based on the H.323 protocol system and, in particular, to a method and system for transmitting a set of short messages, as well as voice communications, between Internet phones using the H.323 protocol system.
2. Related Arts
Telephone networks generally allow wired or wireless subscribers to make voice communications with each other, while data communication networks allow the subscriber to perform various data or information transmissions, as well as voice communications. Further, so-called Internet phones capable of making domestic or international telephone calls via the Internet on data communication networks have been recently in wider use due to their much more economical telephone charges (in particular, in relation to any international calls) compared to charges incurred in using regular telephones.
The H.323 protocol recommended by ITU-T (International Telecommunication Union-Telecommunication Standard Sector) prescribes standards for digital multimedia based communications between wireless terminals, e.g., Internet phones on a packet based network such as the Internet. This protocol may be referred to as “Voice over Internet Protocol (VoIP)” service in the art. The H.323 system is configured to prescribe the entire communications protocol between a variety of network entities substantially constituting one fixed network for multimedia based communications involving the transfer of images as well as voice information, which entities may include Internet phones, a gateway, a multipoint control unit (MCU) as a terminal, and/or a gatekeeper for performing call admission or address translation.
An H.323 multimedia communication network comprises at least one gatekeeper for generally controlling the H.323 system and a plurality of H.323 terminal equipments, such as a personal computer or an Internet phone optionally connected, via a packet based network, to the gatekeeper. The gatekeeper serves substantially to provide overall control of all operations of the H.323 system, including setting up and management of incoming/outgoing calls, and any other additional services, such as multi-party calling, call forwarding or various call termination services available using the system, in particular, in association with the H.323 terminals and a gateway. For the purpose of effecting digital communications between those Internet phones, the H.323 protocol system generally prescribes a series of authentication messages required to communicate between the Internet phone and the gatekeeper.
In order for an Internet phone of a calling party to make a call to an Internet phone of a called party, the Internet phone of the calling party transmits a call admission request message to the gatekeeper, and the Internet phone of the calling party also provides an address of the Internet phone of the called party, i.e., a telephone number of the called party. Thereafter, in reply, the gatekeeper transmits a call admission confirmation message to the calling party when the gatekeeper retrieves a corresponding Internet protocol (IP) address of the called party after searching through a list of IP address registrations, and then sends back the retrieved IP address to the calling party. Then, the Internet phone of the calling party transmits a call setup message to the Internet phone of the called party using this IP address of the called party. The Internet phone of the called party receiving the call setup message sends back a call admission request message to the gatekeeper, and the gatekeeper sends back an admission confirm message to the Internet phone of the called party in response. Then, the Internet phone of the called party receiving the admission confirm message transmits a call connect message to the Internet phone of the calling party. Subsequently, media channel signaling is carried out to establish a communication channel between the Internet phones of the calling party and the called party, and then speech between the two Internet phones is performed.
In the meantime, a short message service (SMS) conveniently utilized to transmit a relatively short message from a calling party to a called party using a mobile terminal is commonly employed in a cellular communication system. Most users accustomed to this SMS function would prefer to use such a short message service in their Internet phones, allowing them to enter and transmit any short messages to an intended called party as necessary. However, with regard to the Internet phones, there is no prescribed protocol for communication of such a short message service via its own network connection, although the Internet phones allow not only voice communication but also video telephone calling.